1. Field of the Invention
This disclosure relates to the monitoring and processing of emissions and waste streams, and more particularly, to monitoring and processing emissions and waste streams containing mercury.
2. Description of the Related Art
Recent environmental awareness has focused on the need to remove harmful mercury emissions from the emissions of systems such as coal fired power plants. These efforts have led to several developments with regards to effective mercury removal techniques. Nonetheless, knowing precisely how much sorbent or other mercury treatment must be utilized so as to better control costs and other aspects of mercury abatement has remained elusive.
All current mercury-monitoring technologies only respond to elemental mercury (as opposed to ionic forms or organic compounds of mercury). Thus, monitoring mercury found in the environment from natural or human-caused sources requires a conversion system and method to convert all forms of mercury present to elemental mercury. Standardized conversion methods are all wet chemical methods currently utilized or approved by various agencies.
However, as an in between method, sorbent traps are the most common method currently implemented for mercury emission determination. Sorbent traps capture mercury from a sample stream from an emission source for a preset amount of time. The trap is then removed and the mercury driven off in one of several methods, captured and analyzed per the procedure for the wet methods mentioned above and the mercury emission rate calculated based on the time in service and sample flow rate. The broad use of sorbent traps is an indication that the mercury Continuous Emissions Monitoring (CEM) technology still is not considered adequate for monitoring.
In typical streams containing mercury, both elemental and ionic forms of the metal exist. The ionic mercury is present as a halogenated mercuric compound (e.g. chloride) and/or mercury oxide. Organic mercury such as methyl mercury also may be present on other processes involving organic wastes from fish processing or the breakdown of organics around mercury containing soils.
In the standard wet chemistry method of converting ionic and/or organic forms of mercury into elemental form, all mercury is trapped and ultimately reduced in a solution to elemental form. This solution is then stripped and sent to an analyzer of one of many methods to determine the elemental mercury concentration of the solution. From this, calculations are performed based on the amount of gasses or other source material to determine the actual mercury concentration in the source. This method is a complicated and lengthy batch process, subject to errors.
Thus, there is a need for a rapid, continuous, dry conversion process that provides reliable, high accuracy results in all common environments from all forms of mercury. This process would allow for better control of conversion chemicals, sorbent, and/or other mercury abatement chemicals.